Salka Gudmundsdottir is a young Icelandic playwright and her show “Breaker” is presently playing at the Cowgate Underbelly. It feels good to be able to commend some new writing which does more than just entertain. I have been lately worrying that I am turning into the troll which lives under the Fringe: a creature which periodically emerges to hurl flamboyant abuse at other people’s plays. “Breaker” does allow my inner troll some grounds for grumbling, but during this play he often rolls over and purrs.

“Breaker” observes a chance meeting between two strangers on a remote and unspecified island. Despite this play’s Icelandic credentials, we are granted the means to locate its setting somewhere in the Highlands; whilst the bleak tragedy which had earlier unfolded on the island may put a British audience in mind of the contemporary “suicide cult” at Bridgend.

The no-nonsense village teacher Sunna (Isabelle Joss) explodes on to the stage in the belief that Danny (Iain Robertson) is trespassing in her school. Just who Danny is and what he is doing remains unclear. He seems grubby and pleasant, but indefinably suspicious. Once we have learned about this island’s troubled past, we may anticipate that he will be soon unmasked as a tabloid journalist. Sunna, for her part, is more recognisably a teacher. With everything girlish about her long dried up, she can change without warning from calm to aggressive authority.

Sunna is not going to have her island’s story exploited for the entertainment of outsiders. It does not greatly aid this emphasis upon secrecy that Sunna’s yelling can be probably heard all over the island. They can surely make out the gist of it over on the mainland. The power of these actors’ four lungs is mildly amazing – it is like an opera without the singing. If Sunna is adamant that her story will remain untold, we can only sit still and hope that she will not suddenly notice us all assembled here in front of her. She would go through the roof!

If I am lapsing into my customary trollishness, I find myself getting some flak in this play. In a display of faintly uncanny omnipotence, Sunna will witheringly rebuke not only Danny but his and my entire disastrous generation of unemployable graduates. It is not even a truthful description of Danny, who turns out to have a mysterious agenda of his own, but it remains an excruciatingly accurate profile of Tychy.

These characters bicker and then warm to each other and then their encounter acquires the mesmerising force and clarity of a thunderstorm. Yet the trouble with this play is that it is ultimately, in the eye of its storm, an allegory. Somewhere below the gale, “Breaker” possesses the bloodless quality of a Socratic dialogue. Its two inquisitive and detached adversaries are trying to work out the world between them. The play is noticeably too long and the weakness of Gudmundsdottir’s writing is that it says rather than shows. The striking stories and performances on stage already convey what the dialogue is still labouring to articulate.

At first these characters seem to compromise or even exchange their own values. Sunna goes back on her certainty that everybody needs “roots” when she is forced to bend the folk story about the “mother of the sea” to suit her own circumstances. Danny, meanwhile, looks to the same story for a greater “narrative,” in contrast to his earlier acceptance of liberated city living. Yet Sunna remains a symbol of the stay-at-home older generation and their jettisoned authority; whilst Danny stands for rebellious and stranded youth. Their fervent kissing may take the audience unexpectedly, but this is actually not sexual, or at least very sexual. The kiss instead leaps at an impossible reconciliation; the momentary solution to an unsolvable puzzle.